1. Field of the Invention
The present invention relates to an apparatus and method for adjusting colors of images projected via an image projector, i.e., a portable communication terminal.
2. Description of the Related Art
Generally, an apparatus having a function of projecting images can project the image at different directions designated by a user. The image projecting apparatus typically displays image data, which are stored in a memory, or image signals, which are input through an image input terminal, on a screen. A white wall or a flat surface with a certain color may be used as a screen.
Such an image projector generally has a distinguished characteristic from an internal display unit, such an LCD. In the internal display unit, a necessary setting can be easily performed, and colors of the image may be effectively displayed using set values. However, an external display unit such as an image projector is affected by the environment in which colorful images is projected, for example, brightness of the external light source, color of a screen, etc. The projection condition can affect the quality of projected images, especially in the image projector, such as a portable terminal, when used in a moving environment.
The portable terminal in today is recognized as a multi-entertainer, which provides users with a variety of information on life and culture, for example, Internet shopping, phone banking, photographing, watching broadcast, entertainment, biological diagnosis, etc. as well as a means for communication. In order to realize various contents, such as moving pictures, movies, three-dimensional games, etc., more multimedia devices such as a digital camera, a Digital Multimedia Broadcasting (DMB) system, a MP3 player, etc. are miniaturized and embedded in a portable terminal.
Now, there are efforts to install a function of a general beam projector to the portable terminal while overcoming the limitation of size limit in the portable terminal, so that a user to watch movie or to play a game. However, a hardware-technical problem including a lens of a general image projector, a low luminance according to the miniaturization of a backlight, and a distortion of projected image, and a distortion problem of projected image caused by effect of circumstance and color quality of the portable image projector have been a roadblock to the development of these products.
Unlike a general Liquid Crystal Display (LCD) or a Digital Light Processing (DLP) in which a light source and a screen are fixed, the portable image projector provides images, the quality of which is affected by the background color of an object on which the images are projected, or the surrounding light sources because of frequent movement of the portable terminal. To this end, a color correction technology has been developed, which considers the color of an object on a projection screen when a portable image projector is implemented.
As an example of the conventional color correction technology considering a background color, there is a background color correction technology using a color adaptability of human eyesight for a general projection equipment (for example, Masato Tsukada, “Projector Color Reproduction Adapted to the Colored Wall Projection” CGIV 2004). This method is a technology in which a color adaptable model of human eyesight is introduced into a color space of CIEXYZ in order to correct the background color. However, this method has many errors in the correction of the background color due to an error in eliciting RGB output value and CIEXYZ value of a color sensor. Particularly, it is difficult to realize the color correction technology in the CIEXYZ color space in real-time because of an amount of calculation in gamut mapping and device characterization procedures.